This invention relates to a method of producing ceramic manifolds having at ends thereof of a plurality of branch pipes to be used for thermally insulating exhaust channels of gasoline engines, diesel engines and the like.
Ceramic pipes such as port liners for thermally insulating exhaust channels or exhaust manifold liners have openings on an engine side and an exhaust pipe side, respectively, and are used to maintain the temperature of high temperature engine exhaust gases passing therethrough. Such ceramic pipes are generally complicated in shape. Particularly, ceramic pipes for four valve engines (which are more frequently being used) are very complicated in shape and have a plurality of branch pipes extending from ends of the ceramic pipes.
Such ceramic pipes have been produced with split molds by drain casting. Even though they are formed in exact shapes, they are likely to deform during firing after the forming process. Particularly, in the case of main ceramic pipes having a plurality of branch pipes long extending from ends of main pipes, the plural branch pipes deform by gravity so as to change spaces between the branch pipes to make cast-in bonding of the ceramic pipes in cylinder blocks difficult.